But doesn't Android already need to address all those issues, regardless of whether the manufacturer chooses to have an SD card slot on a particular device?

Yeap, but a lot of people claim that Android is too hard to use.

And there are a lot of ways to get around the problem. Android allows you to place apps on a removable SD card, but I don't think that's necessary. Most people talk about placing data (like movies) on the card, not software. Or look at computers: very few people try to place software on removable drives and very little software will run on removable drives (at least in the world of Windows). People rarely complain about that either!

So I think the original post was bringing up issues that very few people would even care about.